Electron discharge device having two sections



N. P. GOWELL A a-i116, 1957 4 Sheets-Sheet 1 Filed Dec.

INVENTOR A we): NEY

N/LES R GOWELL April 6, 1957 N. P. GOWELL 2,789,243

ELECTRON DISCHARGE bEVICE HAVING TWO SECTIONS Filed Dec. 31, 1948 4 Sheets-Sheet 2 jamma; 36 l 7 Z6 I 3% AVC v .W

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AITQRNE V April 16, 1957 N. P. GOWELL I ELECTRQN DISCHARGE DEVICE HAVING TWO SECTIONS 4 Shets-Sheet 5 Filed Dec. 31, 1948 FIG 4',

FIG. 3

. INVENTOR N/LES P GOWELL BY 4% 91, gm ATTU/NEY Ap 16, '1957 N. P. GOWELL summon DISCHARGE DEVICE HAVING TWO SECTIONS 4 Sheets-Sheet 4 Filed Dec. '31 1948 m w n 8. 5 2 NO G WM. Rim 5 m, M 5m M 5/ xx 2R. N 0 2 T m m 5 m 6 5 m \f/ m m m m m w m w m o ATTORNEY On the opposite side of the filament 12 from the triode section 11 is the pentode section 10. The grid network 22 of the pentode structure is supported by a pair of rods 23 which are supported by the mica end members 17 and 18 and positioned on either side of the filament 12 and parallel therewith. Stretched between these rods on the side of the filament opposite the triode section are the series of equally-spaced parallel wires which form the network of the grid 22. One of the rods 23 is connected to a lead-in member 5.

Adjacent to grid structure 22 and on the opposite side thereof, from the filament 12, there is a screen grid structure comprising another pair of rods 24 around both of which 'is wrapped a wireto form a screen grid network 25. Both the wires of the grid structure 22 and the screen structure 25 are welded to their respective rods. One of the rods 24 is secured to a lead-in conductor 6.

Adjacent the screen grid structure 25 and on the opposite thereof, from the grid structure 22, there is a suppressor grid 26, comprising a channel-shaped member having a rectangular slot 26a cut in the bottom of the channel 26. The suppressor grid 26 is supported by the mica end pieces 17 and 18 and has the sides of its channel shape extending toward the rods 24. The suppressor member 26 is tied to the filament below the bottom mica support 18 by a strap 27.

Adjacent the suppressor grid 26 and on the opposite side thereof, from the screen grid structure 25, there is a plate electrode 28 which is similar to the support member on the opposite side of the triode structure. This plate electrode 28 is a channel-shaped member slightly smaller than 26 and having no hole in its channel shape. The sides of the channel extend toward the rods 24. The plate 28 is attached at its bottom end to a lead-in member 7 and is supported by the end pieces 17 and 18.

The holes in the upper and lower mica support members which engage the suppressor grid 26 and plate electrode '28 consists of a modified H-shape. The two upright legs of the H are slightly triangular, and engage tabs on the suppressor grid 26 and plate 28, respectively. The crossbar of the H is quite thick and the purpose of the hole configuration is to produce a firm frictional fit between the electrodes 26 and 28, and the'mica support pieces 17 and 18. The electrode 15 on the opposite side of the tube from plate 28 engages diamondshaped holes in the mica support 17 and 18 to produce another frictionalfit, while the rods 16, 20, 23 and 24, which support various grid and plate structures frictionally engage round holes in the mica support pieces, thereby rigidly maintaining proper spacing between the various elements.

Above the upper support member 17 there is a getter strap 29 which is welded to an upper tab of the plate 28 and bent to extend over the tops of the other electrodes in the system. This strap contains getter material, in two small detents 30 in the strap, which is used during the manufacture of the tube to clean up undesired gases in the interior of the tube.

While the electron source herein shown consists of two filament wires which are spaced slightly apart, it is to be understood that any number of wires could be used, or indeed a cathode of the indirect heater type can be used. Further, the particular details of'the structure described herein which are used to produce tubes of the subminiature type are by way of example only, and any size tube with various modifications in the spacing, position, and number of electrodes can be used.

Briefly, the operation of the system of the two sections is as follows.

The pentode section 10 is connected as an R. P. amplifier and the triode section 11 is connected to a separate oscillatory circuit.

The grid 14 is very close to the plane of the filament structure 12; for example, a spacing of .010" therebetween produces good operating characteristics for the subminiaturetube herein described. Now due. to the proximity of the grid structure 14 of the triode 11 to the filament 12 and to the space between the filament 12 and the first grid structure 22 of the pentode section 10, fields produced by voltages on the grid structure 14 of the triode section 11 will control the current to a substantial degree in the pentode section 10. Thus it may be seen that voltages in the triode section will modulate signals being amplified in the pentode section. This effect, of one element in one section of a-tube' exerting a control over the current how in another section'of the tube, may be termed interaction control, and the term interaction control is so defined wherever it appears throughout the specification and claims.

Referring now to Fig. 5 there is shown a circuit diagram of a frequency converter using this tube. In this system a signal is received on antenna 31 and-fed through an R. F. transformer T to the grid 22-of the pentode section 10 of the tube. The secondary of the transformer T1 is tuned by a variable condenser 32 connected thereacross. The screen grid 24 of the pentode section is connected to B+. The plate 28 of the penode section is connected through a primary 6f an I. F. transformer T2 to B+. The I. F. transformer T2 may be tuned to any desired frequency, for example, the standard 455 K. C. I. F. band, by condensers 36 and 37 connected across the primary and secondary windings, respectively, of said transformer.

A suitable potential A+ is applied across the filament 12, one side of which is grounded. The plate 16 of the triode section 11 is connected to 13+ through the primary of a feed-back transformer T3. The secondary of the transformer T3 is connected from ground through a D. C. blocking condenser 33 to the grid 14 of triode section; The grid 14 of the triode section is connected to ground through a suitable grid leak resistor 34 of, for example, 50,000 ohms. The secondary of the transformer Ta is tuned by a variable condenser 35 connected thereacross which is ganged to the variable condenser 32 for tracking the tuning of the R. F. and oscillator circuits in conformance with standard 'superhetrodyne receiver practice.

The grid 22 of the pentode '10 is connected to ground through the secondary of the transformer 1. This grid might be connected to an automatic volume control buss through the secondary transformer T1 rather thanto ground since this tube exhibits variable conversion gain characteristics.

It may be seen from the circuit that the triode section 11 has no external alternating frequency connection with any of the electrodes of the pentode section. Rather the grid 14 of the triode section produces a field which extends into the space between the filament lzand the 7 grid 22 of the pentode section, thus coupling oscillations from the triode section into the pentode section. This coupling is suflicient that, with approximately twenty-five volt bias on the grid section 14, the pentode section is substantially cut off. Therefore, when theR. M. S; oscillating voltoge in the triode section reaches approximately twenty volts, intermodulation occurs in the pentode section, thus heterodyning the frequency generated in the oscillating triode section 11 with the incoming frequency from the antenna 31. Condensers 32 and 35 are so ganged that the difference frequency between the incoming frequency to the grid 22 and the oscillating frequency of the triode section 11 is equal to an intermediatefrequency to which the L-F. transformer Tz'is tuned. Therefore, signals coming in from the antenna 31 are converted to an intermediate frequency.

Referring now to Fig. 6 there is shown a plot of the operating characteristics'of a tube built in conformance with this invention. Along the ordinate of the graph there is plotted the root means square voltage of the oscillator frequency appearing on the grid '14 of the triode section 11. On the abscissa scale on the let of the graph there is plotted conversion tranconductance Go in micro ohms. This is shown by curve 35.

it may be seen that curve 35 remains substantially con stant at a value of approximately 90 rnicroohms for all values of the oscillating voltage above 16 volts. Since conversion transconductance multiplied by the total load resistance, which is equal to the plate resistance of the pentede in parallel with external resistance of the pentode plate circuit, equals the gain of the converter stage, curve 35 shows the characteristic of the gain of the converter with respect to the oscillator voltage. This gain remains substantially constant over the range above 16 volts of the oscillator. However, as shown by the dotted line 37, which represents the characteristic transconductance of a pentagrid converter circuit, this gain drops down after a peak has been reached with the result that there is no region over which constant gain may be had. Therefore, applicants improved converter may be manufactured in large quantities, with a considerable variation in the values of the component parts, and still result in a product wherein all the converter stages have the same gain. This is due to the fact that, while variation in circuit components such as transformers, condenser and resistors affect the magnitude or" the oscillator volta e, this variation in oscillator voltage will not afiect the gain of the stage if the oscillator voltage is normally designed to operate well out on the fiat portion of the curve 35, for example, at a normal oscillator voltage of 25 volts S.

Curves 38, 39 and 4% are curves of the oscillator plate current, the pentode plate current, and the pentode screen current, respectively. The abscissa scale for these curves is found on the right-hand side of the graph and is plotted in milliamperes. it may be seen that the total of the currents of these curves is extremely low, less than .7 mil, for all values of the oscillator voltage.

Other and further modifications to this invention will be apparent to those skilled in the art without departing from the spirit or scope of the invention. For example, any desired oscillator circuit may be used such as a i-iartley, or Colpitts, and any desired number of electrodes be used in either the oscillator or converter sections of the tube. Further, the interacting field may be produced by other electrodes than the ocillator grid, for example, an oscillator plate screen grid, suppressor grid, cathode, or any other electrode in the oscillator section.

Therefore, applicant desires a broad interpretation of the claims commensurate with the scope of the invention within the art.

What is claimed is:

1. An electron discharge device comprising a plural filament cathode having elements lying generally in a first plane, a first anode and grid support means on opposite sides of said first anode all disposed generally in a second plane substantially parallel to said first plane, a second anode lying to the opposite side of said cathode from said second plane, a control grid mounted on said sup port means and being bowed in shape to dispose an intermediate curved portion closely adjacent said cathode between said cathode and said first anode and having no part between said cathode and said second anode, the proximity of said control grid to said cathode being such that its normal control field extends into the region between said cathode and said second anode and thereby it controls the flow of electrons to both of said anodes.

2. An electron discharge device comprising a plural filament cathode having elements lying generally in a first plane, a first anode and grid support means on opposite sides of said first anode all disposed generally in a second plane substantially parallel to said first plane, a second anode lying to the opposite side of said cathode from said second plane, a control grid mounted on said support means and being bowed in shape to dispose an intermediate curved portion closely adjacent said cathode between said cathode and said first anode and having no part between said cathode and said second anode, and proximity of said control grid to said cathode being such that its normal control field extends into the region between said cathode and said second anode and thereby it controls the flow of electrons to both of said anodes, said grid having an additional part extending between said supports across the side or" said anode away from said cathode.

3. An electron discharge device comprising a plural filament cathode having elements lying generally in a first plane, a first anode and first grid support means on opposite sides of said first anode all disposed generally in a second plane substantially parallel to said first plane, a second anode lying to the opposite side of said cathode from said second plane, a first control grid mounted on said first support means and being bowed in shape to dispose an intermediate curved portion closely adjacent said cathode between said cathode and said first anode and having no part between said cathode and said second anode, the proximity of said first control grid to said cathode being such that its normal control field extends into the region between said cathode and said second anode and thereby it controls the flow of electrons to both of said anodes, second grid support means disposed on opposite sides of said cathode in said first plane, and a second control grid mounted on said second support means and extending between said cathode and said second anode.

Reterences Cited in the file of this patent UNITED STATES PATENTS 

